Process for reacting a diolefin and a furfural



J.. c. HILLYER ETAL 2,898,347

Aug. 4, 1959 PROCESS FOR REACTING A DIOLEFIN AND A FURFURAL Filed July 5, 1955 United States Patent@ PRocEss FOR REACTING A DIoLEFm AND A i FURFURAL John '-C. Hillyer and James T. Edmonds, Jr., Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Application July 5, 1955, Serial No. 519,882 8 Claims. (Cl. M50-346.2)

This invention relates to a process for interacting a diolein and a furfural. improved process for synthesizing a butadiene-furfural cotrimer.

It has been recently disclosed in .U.S. Patent No. 2,683,151, issued July 6, 1954, that a diolen such as 1,3-

butadiene and its immediate homologs may. be reacted 2,898,347 Patented Aug. 4, 1959- ICC numerous organic chemicals. Still other uses will be apparent to those skilled in the art.

In one of its aspects, it relates to an atoms per molecule.

In producing this aldehyde rev During the reaction of the dioleiin and the `furfurallre- Y actant, the same DielsAlder type reaction is also responsible for the formation of the butadiene dimer vinylcyclohexene. The condensation of butadiene with itself to form butadiene dimer proceeds at a much greater rate than the condensation of butadiene with furfural. Furthermore, the formation of butadiene dimer is not an equilibrium reaction at the temperature of reaction, and its formation greatly decreases the quantity of butadiene available to react with the furfural. It becomes neces- As a diolefn reactant in our process, we prefer to-use aconjugated dioleiin, preferably a conjugated diolefn'having not more than about seven carbon atoms per molecule. Such a diolefm can be referred toas a member of the group consisting of 1,3-butadiene and its immediate ho# mologues and may be reported as having the formula` ...nana

where each R is of the group consisting of hydrogen and an alkyl group having not more than three carbon atoms and at least two R are hydrogen. The furfural reactant employed in the practice of our invention can be referred to as one of the group consisting of furfural and its im. mediate homologues having not more than seven carbon Such a material may be said to be a compound having the formula where each R is of the group consisting of hydrogen and methyl and at least one R is hydrogen. The more commonly used reactants are 1,3-butadiene and furfural, isoprene and furfural, and piperylene and furiural, andthe corresponding dioleiins with methylfurfural.

' The diolefin-furfural cotrimers of this invention are formed by the reaction of two molecules of a diolefn with sary, therefore, if high yields of the desired cotrimervproduct are to be obtained, to increase the reaction of butadiene with furfural while decreasing the competing reac.- tion of butadiene with itself to form butadiene dimer.

In accordance with this invention, a process is proposed whereby these desirable results are obtained.

' 'Ihe following are objects of the invention. n

It is an object of this invention to provide an improved process for reacting a dioletin with a furfural.

Another object of the invention is to provide an improved process for producing 2,3,4,5bis ,(A2butenylene) te'trahydrofurfural by reacting 1,3-butadiene andfurfural.

Another object of the invention is to ,provide an 1mproved process for producing in increased yields a cotrimer of butadiene and furfural.

Still another object of the invention is'to provide a continuous process for synthesizing awbutadiene-cotrimer in which the formation of butadiene dimer is reduced to a minimum.

A further object of the invention is'to produce poly- Acyclic aldehydesy by the reaction of a'dioleiin and a f urfural..

Other and further objects and advantages of the invention willbecome apparent to those skilled in the art upon consideration of theaccompanying disclosure.

The butadiene-furfural cotrimer produced by this invenl tion has many uses. Among these Ythere may Abe' mentioned its use asan insect repellent, asa plasticlzer and/ or V,tackifel for synthetic rubber, as a component in phenolic resins, and as a chemical intermediate for the synthesis of one molecule of a furfural. The aldehyde so formed may be represented by the following structural formula:

where each R is of the group consisting of hydrogen and methyl and at least one is hydrogen, and each R' is of the group consisting of hydrogen and an alkyl group having not more than three carbon atoms with the sum of the carbon atoms in the R'm and in the R',L in each case, not greater vthan three and at least two of the R'm and of vthe 4R1L are hydrogen. The aforementioned reaction 'is' accompanied by a competing reaction, namely, the condensation of the diolefin with itself to form the diolefn dimer, which decreases the amount of diolefn available for reaction with the furfural. As a result, when carrying out the reaction in a batch type operation, the yield of cotrimer, based on diolefn converted, has been found to `berelatively low, e.g., in the neighborhood of 20 percent or less. l

We have now discovered that by controlling the rate of diolen introduction so as to maintain a predetermined pressure ina closed reaction zone containing a furfural heated to reaction temperature, it is possible to obtain a cotrimer yield of from 45 to 50 percent and higher, based on the dioletin reacted. In a broad aspect, the process of this invention comprises introducing adiolen in to a closed reaction zone containing a furfural heated to reaction temperature, and controlling the rate of dirolen introduction so as to maintain a pressure therein between 50 and 150 p.s.i.g., preferably between 75 and 135 p.s.i.g. The cotrimer product formed by interaction of the diolen and furfural can be recovered by distillation of the reaction mixture.

According to one embodiment of the invention, a dioleiin, such as 1,3-butadiene, is introduced into a closed reaction zone containing afurfural, such as furfural itself, heated to a reaction temperature between 200 and 600 F., preferably between V350 and 450 F. Butadiene is charged to the reaction zone at a controlled rate so as to maintain a pressure therein between 50 and 150 p.s.i.g. The butadiene and furfural are reacted for a period between 1 and 50 hours or more, preferably between 5 and 15 hours.

In order to obtain the benefits of this invention, it becomes of primary importance to control the rate of butadiene introduction so as to maintain a reaction pressure in the above-identified range. While the over-all reaction rate may be increased many times by operating at higher pressures, the fraction of the butadiene converted to the cotrimer decreases materially at pressures above 150 p.s.i.g. with a corresponding increase in the fraction of the butadiene converted to thedimer. For example, it has been found that while the over-all reaction rate increased 12fold as the reaction pressure was increased from 100 to 250 p.s.i.g., at 250 p.s.i.g. the fraction of butadiene converted to cotrimer decreased from an average of about 4Z Vpercent to about 17.5 percent while the fraction being converted to the dimer increased from an average of about 43 percent to about 76 percent.

Although the reaction temperature can vary within a wide range, e.g., between 200 and 600 F., and preferably between 350 and 450 F., while still obtaining increased cotrimer yield when operating according to this invention, it has been found to be even more desirable to operate at a reaction temperature between 375 and 425 F. Shorter reaction times are required at the higher ternperatures, but under these conditions an increased amount of furfural is converted to tars and resins. Thus, optimum operating conditions, combining a reasonable reaction rate with the highest selectivity in the reaction of butadiene with furfural toform the cotrimer are between 375 and 425 F. at a pressure between 75 and 135 p.s.i.g.

It is preferredto utilize anhydrous furfural in order to minimize furfural homopolymerizationand the possible formation of lactones. It is, however, Within the scope of the invention to have some water present although it is desirable that the water content be maintained below about 5 percent by weight of the furfural. With regard to the dioleiin reactant, inhibitors such as tertiary butylatechol can be used therewith to inhibit homopolyrnerization of the dioleiin.

Butadiene can be charged to Vthe reaction zone by incremental addition, or the butadiene may be added continuously. In the incremental injection of the butadiene, the butadiene is generally introduced during a certain .part of each hour of operation in amounts sufcient to maintain the pressure in the reaction zone in the desired pressure range. It is preferred, however, to introduce the butadiene in a continuous manner so as to maintain a lpreselected pressure within the reaction zone. The instant invention can be carried out as a batch type process with either incremental or continuous addition of the butadiene, or a continuous process can be utilized. The preferred mode of operation is to carry out the process in a continuous manner. i

A more comprehensive understanding of theA invention may be obtained by referring to the drawing which is a process. Butadiene is pumped from a source, not shown,

into closed reactor 5 through inlet line 6. Reactor 5 is provided with a suitable stirrer 7 which is rotated by a motor, not'shovvn. The butadiene reacts with furfural contained in the reactor and heated lto* the desired reaction temperature as will be described more in detail hereinafter. It is within the scope of the invention to carry out the reaction in the presenceof a solvent such as a paraffnic or aromatic hydrocarbon.

The rate of flzutadiellc introduction into reactor 5 is Y controlled by` means of pressure'recorder-controller which is Yoperatively connected to reactor 5 and to motor valve 9 contained in inlet line 6. The controller is of a type well lrnown in the art which is adapted to supply a pneumatic signal to the motor valve, which is proportional to the pressure in the reactor. As previously described; it is desired to carry out the reaction of butadiene with furfural at a predetermined reaction pressure. Accord,- ingly, the controller is given an index setting corresponding to the pressure which it is desired to maintain within the reactor. ,The controller then operates to actuafe mntor valve 9 so that butadiene-'is introduced into the reactor at the rate required to maintain the set pressure.

The reaction products are removed from thev reactor through line v1p1 :at a rate ldependent-upon 4the setting of motor valve 12 contained in this line. "Motor valve 12 is actuated by a liquid level controller 13 which is operatively connected tofreactor 5. The liquid level controller adjusts valve 172 so as to maintain a predetermined liquid level within reactor'S. By controlling the rate'of withdrawal of reaction products in this manner, the reactants are maintained within thevreactor Afor the desired reaction period; The methods and means used for controlling the rate of butadiene introduction and the rate of withdrawal of reaction products are not a part of the instant invention, but ar'e disclosed and claimed in copending U.S. patent applications.

The V'reaction products withdrawn from -the reactor throug'hline A11 are passed into ash tank 13 wherein the pressiire 'isi reduced from reaction pressure. Unreacted butadiene and some fur'fural and butadiene dimer are thereby flashed from the reaction products, lbeing r moved through line 14. The reaction products are with'- drawn fr om Hash tank 13 through line 16 and passed into fractionator 21 whereinthe butadiene dimei-.is separated from the reaction products. In this separation, the dimer is taken? overhead -as a vapor 'through line 22 and `passed intofal condenser V23 wherein it .is condensed. The con, densate is passed from condenser 23 into accumulator 24 through line 26. The dimer is removed from the accumulator through Yline 27, a Aportion being introduced into fractionator 21 through line 28 as reflux. The remainder of the dimer isreco'veredby means of line `29.Y

The kettle product withdrawn from fractionator 21 comprises urfeural, butadiene-furpfural cotrimer land a small amount of resinous material. The kettle product from `fractionator 2 1 .is introduced into fractionator31 .via line 3 2. .In this fractionator, furfural is taken over,- head through line 33 and passed into condenser A34 wherein itis condensed, the condensate then being introduced into accumulator 36 through line 37. A portion of the furfural removed tfrom accumulator 36 via line 38 is introduced into fractionator 31 as redux through line 39 while the remainder of the furfural is recycled to' rcactor 5 by means of recycle line 41.

Y Recycle line/41 contains a heater 42 through which the I'pfurfural passes `priorto introduction into the reactor. In heater 42, the furfural` is heated -to lthe `temperature at limitativ'eof the invention.

By continuously circulating the furfural in this manner and heating same before injecting into the reactor, it is possible to maintain the desired reaction temperature in the reactor. The rate at which furfural is charged to the reactor is controlled by means of valve 43 contained in recycle line 41. The valve is operatively connected to a ow meter 44 which is given a setting corresponding to the rate at which furfural is to be introduced into the reactor. In carrying out the instant invention, suiiicient furfural is charged to the reactor to maintain an excess therein over that required for the reaction. Line 46 provides means for introducing makeup furfural into the system.

The kettle product recovered from fractionator 31 platform rocker and connected to a Vessel containing pure grade butadiene. The butadiene vessel, which was 1` ttedwith a, sight gauge, was pressurized lwith nitrogen.

The bomb was heated to the desired operating temperature and the butadiene was charged by hand control at such intervals thatA the pressure in the reactor remained within the range of 80 to 150 p.s.i.g.

On the completion of the reaction, the bomb was cooled to room temperature and the pressure was released. The gases were passed through a Dry Ice trap to collect the unreacted butadiene. The liquid portion of the reaction mixture was then distilled and several fractions were col-'- ""lected. At an absolute pressure of about one mm. of

through line 47 comprises the butadiene-furfural cotrimer and a small amount of resinous material. The kettlel product is introduced into fractionator 48 by means ofline 47. In fractionator 48, the desired separation oi cotrimer from resin is made with the cotrimer being taken overhead through line 49. The vaporous cotrimer is condensed in condenser 51,: andthe resulting condensate passed into accumulator 52 by means ofline 53. Aportion of the cotrimer removed from accumulator 52 by line 54 is passed as reux into fractionator 48Vthrougli line/,56. The remainder of the butadiene-furfural cotrimer is recovered through line 57 as theproduct of the process and passed to suitable storage facilities. The resinous material isremoved from the bottom -of the iractionator 48 throughline 58. i i .i

As discussed hereinabove-the process of this invention can bepracticed in a batch as well as a continuous operation.' In a batch type operation, furfural heated to the desired reaction temperature is initially charged into a reactor similar to that shown in the drawing. Thereafter, butadiene is injected into the reactor so as to maintain the pressure therein between 50 and 150 p.s.i.g. The

butadiene can b e either introduced continuously as de- I scribed in conjunction with the apparatus of vthe drawing, or it can becharged incrementally to the reactoras specied periodsv during the reaction time. At the end of the desired reaction period, the reactor is emptiedl and the mercury, the butadiene-furfural cotrimer boils .at about 115 C. The residue from the distillation also `'probably contains some heavier polymers of thecotrimer. The data obtained from three runs, namely A, B and'C, when operating in this manner are summarized in Table II hereinbelow.

The cotrimer, 2,3,4,5bis(A-butenylene)-tetrahydrofurfural, was a straw colored liquid with the empirical formula C13H15O2. The distillation data for the reaction products from run B is set forth in Table I hereinbelow.

reactor effluent passed to a surgeand ashtank. The

pressure in the surge and flash tank is bledA down, e.g. from 150 to 5 p.s.i.g.,L over an extended period of time, e.g.,Y over a period oiaboutftwo hours. Theilash vapors from theV surge and ilash tabla-which comprise essentially butadiene, butadiene dimer and furfural,v may be 'passed to a storage tank for subsequent recycle to the reactor. The liquid material withdrawn from the surge and flash tank is charged to a batch fractionator which operates to separate the material into butadiene dimer, furfural and the cotrimer product. The furfural removed from the batch fractionator can be sent to a furfural storagetank for subsequent recycle to the reactor.

A s analt'ernateAAV procedure, the'unreacted butadiene can be bledfrom Ythe reactor and the liquid portion offthe reaction fractionated or treated as desired.

A more comprehensive understanding of theinvention 'may be obtained by referring to the following illustrative be Vunduly examples which are not intended, however,A to

. EXAMPLE 1Y A sample of furfural was prepared by, d istilling commercial furfural in a lil-inch Vigreux column. The distillations `were done at "l0 to l5 mm. mercury pressure, and only the middle fifty percent of the,v distillate was' The cotrimer was contained in fractions 9 and l0 as shown in Table I. The residue from distillation was an amber-colored resin, soluble in acetonepand assumed to behigher polymers of the butadiene-furfural cotrimer.

Pressur Tem- Weight, pelaure,

Cut gms.

butadiene dimer. intermediate fraction.

furfurel.

intermediate fraction.'

cotrimer traction.

Losses Percent recovered EXAMPLE II Thesamereactants were usedpin this example as in Example I. The furfural (800 gms.) was charged to a steel bomb, sealed and placed in a bathcooled with solid carbon dioxide. After cooling for 20 minutes, the air in the bomb was removed with a vacuum pump and the butadiene was charged to the cooled bomb until the desired weight had been added. The bomb was then allowed to lwarm to room temperature and the contents mixed thoroughly, after which the bomb was placed in a hot oil bath and brought to the operating temperature. At the end of the reaction time, the reaction products were treated in the same manner'as described in Example I. The data obtained frn'ifour runs, namely runs D, E, Fand G, when operating in this manner are summarized in Table II hcreinbeloxV l Q It is evident from an examinationA of the data contained in Table II that by incrementally injecting butadiene so as to maintain a predetermined reaction pressure, the fraction of butadiene cor'ivertedV to cotrimer was materially increased,over-thafoljtinedin the batch rep anions' aaneen Table II Y Butadlene Cotrlmer Butadiene 04H. Se1ee. Y Temp., Time, Charged Yield Convertivity to Run '"F. Hours sion Cotrimer, *s Percent 2. Percent:

Gins. Moles Gms. Moles .Arcore-'Au contained soo furfurai.

1`Furiur eleontained 1.64 percent Water.

l Resin' boiling above cotrimer .was assumed to be the polymerization product'oithe recovered divided Yby the total butadiene charged.

EXAMPLE III A one gallon, stirred autoclave was used as the reactor in this example. The reactor was provided with an in- -ternal cooling coil, stirrer, thermocouple well and a product blowout tubewhich extended to the bottom of the reactor. The reactor was heated by means of surrounding heating bars built within the reactor assembly. The amount of cooling medium supplied to the cooling coil was determined by manual control of a valve in the line supplying the cooling medium to the coil. Dry, distilled furfural was pulled by vacuum into the cold reactor through the 'blowout tube. The reactor was then heated, and when the desired reaction temperature reachedinhibitorfree butadiene was pumped into. the reactor. Precautions were taken to ensure thatno air was present in the reactor. After suflicient butadiene was charged to the reactor to achieve the desired operating pressure, the reactor pressure was maintained within plus or minus 2 pounds of the desired'operatng'V pressure by means of a suitable arrangement of control apparatus.

The amount of butadiene added to the rea'ctorfwas determined by occasional weighing of the butadiene charge tank. When the desired amount ofi-butadiene had been added, the run was terminated. Heat to the ,reactor Twas then shutoff andc'ooling water passed through the internal cooling coil to cool the reaction mixture. Cooling was terminated when the reactor pressure dropped to about 30 p.s.i.g., The reaction mixture was collected in a series of condensing units, including a Dry Ice acetone trap. The reaction mixture was removed from the reactor at such a rate` that all of the butadiene vapors were condensed in the Dry Ice trap.

Distillatio'n `of the normally liquid fraction of the ref actor product was done in two steps. First, butadiene,

- dimer and most of the fururalwas taken overhead in l drainage Abefore each transfer.

a 25 mm. O.D. Hyper-Cal column. When pot product occupied less than 500 ml., it was transferred to a 500 ml. ask and distilled in a smaller column packed with Heligrid packing. Care was taken to allow good column After emptying the re actor and recording the weight of unreacted butadiene collected, the liquid product mixture was kept at Dry Ice temperatures until it could be charged, still cold, to a tared fractionation pot. Heat was applied slowly at first during fractionation until pot temperature reached` room temperature and then the mixture was heated at a rather fast rate Butadiene evolved was collected in a Dry Ice cooled trap and weighed. The pot was heated until butadiene dimer (13.1.A 129-30 C.) began retluxing.

vYields of each component were calculated on the basis of butadiene reacted. Pot residue was assumed to be 100 percent cotrimer resin. summarized data for the runs are tabulated in Table III.

TabIeIII eUMMARIznD DATA snow-:No EFFECT oF PRESSURE, TEMPERATURE, AND WEIGHT RATIO 0N BUTA,

DIENr: 'CONVERSION To coTRIMER Operating Conditions Ave. Butadiene Rates, Run No. Wt. Ratio,4 Recipe, gms. Gms. Bd. Per Kg.

Temp., F. Pressure, Run Dura- Butadiene: Furfural Per Hour p.s.1.g. tion, Hours Furtural Butadlenel Furfural Feed Reaction 400 100 1. 6 1:14. 7 68 1, 000 69. 4 42. 4 400 100 3. 7 1:8. 35 120 1, 000 44. 6 32. 0 100 7.2 1:5.4 250 1,350 37. 3 28.8 400 100 7. 2 1:4. 4 228 1,000 39. 7 3l. 8 400 100 14. 75 1 :2. 43 412 1, D00 30. 9 27. 9 400 100 14.5 1:2.24 446 1,000 34.5 30.8 400 37. 0 1:2. 60 384 1, 000 12. 2 10. 4 400 150 7. 5 1:1. 53 651 1, 000 97. 6 86. 9 400 250 2. 5 1:1.13 888 1. 000 396. 0 355. 0 425 15.0 1:2. 52 396 1,000 29.0 26.4 375 100 18.0 1:2. 24 447 1, 000 28. 2 24. B

Footnotes on next page. Y

yrabia111--,comme I 7 Y' Y 'Y i Product Distribution and Results Buta- Eiuent Composition, weight percent o -Butadiene Yields, wt. percent of Furfural Yields, wt. Lbs. Run diene Furturai plus reacted Butadiene Butadiene Reacted percent cotrmer No. Con- Charge (Butadiene Free) per lb.

version, Butawt. y f l diene percent Dinner OOD 2 Fur- Co- Resin Dimer COD 2 Co- Resin Reeov- Co- Resin Reacted fural trimer trimer ered triiner 61. 2 2. 5 (a) 89. 0 5. 4 1. 7 39. 8 45. 7 17. 0 95. 4 2. 7 0. 8 0. 852 71. 8 4. 5 (3) 83. 5 8. 5 3.- 5 41. 7 41. 7 16. 6 94. 2 4. 4 1.8 0. 782 77. 3 6. 8 76.0 13.0 3. 8 43. 2 (t 44. 0 p 12.8 90. 0 7. 2 2. 1 0. 770 80. 1 6. 9 (i) 70. 0 14. 7 6. 7 37. 4 (a 42. 3 19. 3 86. 2 8. 5 3. 9 0. 794 90.3 13. 6 (3) 55.6 22.3 6. 6 47.0 (s 40. 8 12. 2 79. 1 14.9 4. 4 O. 770 89. 3 14.3 (3) 52. 3 24. 6 4. 9 47. 6 (3) 43. 5 8. 9 77. 9 17. 2 3. 9 0. 818 85. 3 7. 6 1.0 52. 7 21. 6 14. 5 27. 2 3. 4 41. 1 28. 3 72. 9 14.0 9. 5 0. 730 89.0 25.8 1. 7 47. 0 17. 5 6. 5 64. 0 4. 1 23. 3 8.6 75. 9 13. 3 4. 9 0.424 89. 7 33. 6 2. 9 43. 0 15. 7 4. 0 70.3 6. 1 A17. 6 ,4. 5 81. 4 13. 8 3. 6 0.328 91. 1 7. 3 1. 3 53. 6 22. 4 13. 6 26. 4 4. 7 42. 8 26. 1 74. 8 14. 7 8. 9 Y0; 762 88.0 12.9 1.8 53.0 24. 6 6. 9 40. 9 5.8 41. 6 11. 7 74. 5 16.5 4.6 0.755 l 1 Butadiene reacted i Cyclooctadiene. 8 Included in dimer fraction. .Reactants.

An examination of the data set forth in Table III indicates that varying the butadiene to furfural ratio had very little effect on selectivity or reaction rate. Pressure had a very marked effect on results, the over-al1 reaction rate increasing 12-fold as pressure increased from 100 to 250 p.s.i.g. At 250 p.s.i.g., however, the fraction of butadiene converted to cotrmer dropped from an average of about 42 percent to about 17.5 percent, and the fraction converted to dimer increased from an average of about 43 percent to about 76 percent.

It will be apparent to those skilled in the art that various modifications of the invention can be made upon study of the accompanying disclosure. Such modications are believed to be clearly within the spirit and scope of the invention.

We claim:

1. A process for producing an aldehyde having the formula H H a temperature in the range of from about 200 F. to

R,m R R R, about 600 F. for a period of time between about 1 and 50 hours; controlling the rate at which said 1,3-butadiene R'm? ll (511' 45 is introduced into said reaction zone so as to maintain av 121...b C C 0-115, pressure therein between about 50 and 150 p.s.i.g.; and R,m O/1|,-\O/ \C R,l recovering from said reaction zone reaction products I comprlsing 2,3,4,5bis (A2 butenylene) tetrahydrofurwhere R is selected from the group consisting of hydrogen and methyl and at least one R is hydrogen, and R is selected from the group consisting of hydrogen and an alkyl group containing not more than three carbon atoms with the sum of the carbon atoms in the Rm and n the RQ, in each case not greater than three and at least two of the Rm and of the R2, are hydrogen, which comprises introducing a conjugated dioleiiue hydrocarbon, having not more than seven carbon atoms per molecule and the formula Rl Rl Rl $1 H- :tiza-H Where R is selected from the group consisting of hydrogen and an alkyl group having not more than three carbon atoms per molecule and at least two R"s are hydrogen, into a closed reaction zone containing a furfural having not more than seven carbon atoms per molecule and the formula pressure in said reaction zone is between about 50 and 150 p.s.i.g.; reacting said dioleiin hydrocarbon and said furfural at a temperature between about 200 F. and 600 F.; controlling the rate at which additional diolen hydrocarbon is introduced into said reaction zone so as to maintain the pressure therein between about 50 and 150 p.s.i.g.; and recovering from said reaction zone reaction products comprising said aldehyde.

2. 'Ihe process of claim 1 in which said dioleiin hydrocarbon and said furfural are reacted at a temperature between about 350 and 450 F. and said diolefin hydrocarbon is introduced into said reaction zone at a rate such as to maintain a pressure therein between about 80 and 135 p.s.i.g.

3. A process for the production of 2,3,4,5bis (A2-butenylene)-tetrahydrofurfural which comprises introducing 1,3-butadiene into a closed reaction zone containing furfural; reacting said 1,3-butadiene with said furfural at tural.

4. The process of claim 3 in which said 1,3-butadiene and said furfural are reacted at a temperature in the range of from about 350 F. to about 450 F. for a period of time between about 5 and 15 hours and said 1,3-butadiene is introduced into said reaction zone at a rate such as to maintain a pressure therein between about 80 and 135 p.s.i.g.

5. A process for the production of the cotrmer of 1,3-butadeneand furfural which comprises continuously introducing 1,3-butadiene into a closed reaction zone containing furfural; reacting said 1,3-butadiene with said furfural for a period of time between about 1 and 50 hours; controlling the rate of butadiene introduction so -as to maintain a pressure in said reaction zone between about 50 and 150 p.s.i.g.; removing reaction products from said reaction zone and passing same into a flash zone; ashing vapors comprising unreacted 1,3-butadiene from said reaction products in said flash zone; passing butadiene-free reaction products from said ash zone into a rst separation zone; separating butadiene dimer from said butadiene-free reaction products in said irst sepa- R-c--o-R o n ration zone; recovering a stream comprlslng furfural, O\ /C the product cotrmer and a resinous material from O H said iirst separation zone; passing the last mentioned where R is selected from the group consisting of hydrogent and methyl and at least one R is hydrogen until the stream into a second separation zone; separating furiiural from the materials in said second separation zone; heat zone to a temperature in the range of from about 200 F. to 600 F.; recyclingus'aid heatedwfurrfuralmto saidfrey action zone; recovering a stream comprisingthe product cotrimer and resinous materialfrom said secondseparation zone; passing said last-mentioned stream into afthird separation zone; and recovering said cotrimer from said third separation zone as a product of the process.

6. The process of claim 5 in which said 1,3-butadiene and said furfural are reacted for a period of time in the range of from Aabout 5 to 15 hours; said 1,3-butadiene is introduced into said reaction zone at a rate such asto maintain a pressure therein between about 80 and 135 p.s.i.g.; and said recycle'furfural is heated to a temperature in the range of from about 350 F. to about 450 F. p.s.i.g. prior to introduction into said reaction zone.

7. In the process of producing a conjugated dienefurfural cotrimer by reacting a conjugated diene with furfural in a closed reaction zone at a temperature in the range of about 200 F. to about 600 F., the im- 4..prtjr/erneut comprising introducing the furfural to said 'reactionfzona introducing said diene to said reaction zone ata rate VAto maintain the Vpressure in said zone in thsfras 'SOQQS--gf t0 1,50 P-Si-g- @ed thereafter fecovering from said reaction zone reaction products comprising said conjugated diene-furfural cotrimer.

8. The improvement of claim 7 wherein the conjugated diene contains 4 to 7 carbon atoms per molecule V'and the furfural contains 5 to 7 carbon atoms per molecule.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES Hillyer: Ind. Eng. Chem., vol. 40, pp. 2216-2220Y 

3. A PROCESS FOR THE PRODUCTION OF 2,3,4,5-BIS ($2-BUTENYLENE)-TETRAHYDROFURFURAL WHICH COMPRISES INTRODUCING 1,3-BUTADIENE INTO A CLOSED REACTION ZONE CONTAINING FURFURAL; REACTING SAID 1,3-BUTADIENE WITH SAID FURFURAL AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 200*F. TO ABOUT 600*F. FOR A PERIOD OF TIME BETWEEN ABOUT 1 AND 50 HOURS; CONTROLLING THE RATE AT WHICH SAID 1,3-BUTADIENE IS INTRODUCED INTO SAID REACTION ZONE SO AS TO MAINTAIN A PRESSURE THEREIN BETWEEN ABOUT 50 AND 150 P.S.I.G; AND RECOVERING FROM SAID REACTION ZONE REACTION PRODUCTS COMPRISING 2,3,4,5-BIS($2 - BUTENYLENE) - TETRAHYDROFURFURAL. 